Normal Spirilloxanthin Pathway

Spirilloxanthin pathway (normal spirilloxanthin, unusual spirilloxanthin, spheroidene, and carotenal pathways). 

The Chromatiaceae have either the spirilloxanthin pathway (normal spirilloxanthin, unusual spirilloxanthin and carotenal pathways) or okenone of the okenone pathway except for one species, Tea. halophila, which has both pathways (Tables 1 and4). Even in the same genus, some species have the spirilloxanthin pathway and others have the okenone pathway. Therefore, the carotenogenesis pathways are not well related to the bacteria s classification in the Chromatiaceae. 

Carotenogenesis of the normal spirilloxanthin pathway is found in a large number of species of purple bacteria Rhodospirillaceae, Chromatiaceae and Ectothiorhodospiraceae (Tables 3-5). Spirilloxanthin is a symmetrical compound containing the methoxy groups at C-1 and C-1 and additional double bonds in the C-3,4 and C-3",4 positions. It has 13 conjugated double bonds (Fig. 4). 

When one enzyme of the normal spirilloxanthin pathway is lacking or is present with reduced activity, the composition will be expected to change. Some species have indeed been reported to have such unusual compositions (Tables 3-5). Lycopene is... 

The tertiary methoxy and the cross-conjugated aldehyde groups have been found only in the carotenals of the purple photosynthetic bacteria, and the position of the aldehyde group in 1 0 is at C-19 instead of at C-20 as in the known carotenals. The half moieties of their molecules may be synthesized via a pathway of the normal spirilloxanthin series. The other half may be formed by cyclization and hydration as in 8 (FIG. l). 

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